Answer: That is very perceptive. I hadn't really thought of it before, frankly, but now that you mention it, when I think of recitative what I hear in my head is that typical arpeggiated first-inversion triad that so often begins a phrase. Not all passages begin this way, of course, but it's associated with a change of mood or subject; a transition of some kind.

This goes way beyond the baroque; it's a tradition. Robert S. Hatten, in his Musical Meaning In Beethoven, thinks the first inversion triad in recitative is "interpreted as a new dominant cueing a sudden tonal shift, corresponding to a shift in thought or utterance." And it does seem that the arpeggiated chord that starts on its middle note has a sort of uncertainty to it. I'm not sure whether this is habit born of custom, or whether the custom is itself based on some deeper psycho-acoustic basis - but when you hear the first inversion triad arpeggiated that way it does seem to say something that in language might be expressed as: "What about this:" or "Listen:" That's what Hatten means in calling it a "dominant" - a dominant has an introductory function.

So it isn't so much a theological rationale as a psychological one. And as always with psychological effects in music it's hard to tell which came first: is the device effective because it's traditional, or is it traditional because it's effective? My sympathy goes to the latter; I think devices become traditional because they work, and then tradition amplifies the effect.